If I buy a book today, I'll still be able to go back to it in five, ten, twenty years. I can take it off the shelf, go to the page in question, and acquire the information. It just works.
With an eBook, the format is really tied to the times in which it was issued. The format will have evolved into something unrecognizable or disappeared altogether, and with it, the support to read it. It's not really an issue for crappy novels that are read-and-forgotten, but it is for one who prides himself in his library.
Unlike music and video where advances in the medium resulted in an improvement of the content itself, the same can't truly be said of text. Yes, it is more convenient to have a stack of eBooks in one's pocket, but the words are the same whether they're printed or on an eInk display.

I adore words, but let's face it: books suck. More specifically, so many beautiful ideas have been helplessly trapped in physical made-of-atoms books for the last few centuries. How do books suck? Let me count the ways: They are heavy. They take up too much space. They have to be printed. ...